Patent Application
20150034894
This invention relates to devices that dissipate gravitational potential energy via friction in devices that travel along ropes. More particularly, the invention relates to a device that improves a powered rope ascender's ability to smoothly descend a rope in a less damaging way while a heavy load is attached to the powered ascender.
Powered rope ascenders are gaining use in many industries including industrial access, rescue, and military operations. By using a powered motor attached to a climbing mechanism, they allow users to lift heavy loads along standard lines such as climbing ropes. Powered ascenders are also typically reversible—by reversing the direction of the motor (often after first releasing a safety brake), they can descend lines using the same mechanism as is used to climb. However, the way that powered ascender climbing mechanisms are sometimes constructed can, under some circumstances, impart damage to a rope when the ascender is used to lower a load along a rope. Sometimes a rope will also damage the climbing mechanism.
These drawbacks of using a powered ascender to descend along a rope with a heavy load attached can be magnified when descending along ropes or lines of small diameter. The relatively smaller amount of sheath available covering a 7 mm diameter rope, for instance, will provide reduced protection against the abrasion caused by the climbing mechanism in descent as compared to a larger 11 mm diameter rope whose sheath is proportionally thicker. Much work has gone into climbing mechanisms to increase their efficiency and efficacy while reducing their wear upon the ropes they climb, but fundamentally if they are to function as effectively as they must for climbing purposes, they will provide sub-optimal results when descending, particularly when compared to purpose-built devices for lowering along ropes such as rappelling devices and brake bar racks.
It can therefore be an object of the present invention to provide a device that can be used in conjunction with, or even incorporated into, a powered ascender such that the powered ascender may lower loads along the ropes it climbs and reduce or eliminate the damage the climbing mechanism would otherwise impart on the rope while it descends it. By reducing or eliminating the mechanical wear the ropes experience, the descending device could be said to be assisting the powered ascender in towering or descent, hence the nomenclature “frictional descent assist device.”
It can be another object of the present invention to provide a device that provides assisted descending functionality along a range of rope diameters including ones smaller than 6 mm in diameter, larger than 11 mm in diameter, and in between.
Other objects and advantages of the present invention will be apparent to one of ordinary skill in the art in light of the ensuing description of the present invention. One or more of these objectives may include:
The invention provides a descent assist device that preferably accomplishes one or more of the objects of the invention or solves at least one of the problems described above.
In a first aspect, a powered rope ascender operational in ascending and descending modes is provided. The powered rope ascender includes a reversible drive source and at least rotating rope pulling jaw. The jaw is connected to the reversible drive source so as to be rotated in a first, ascending direction and a second, opposed descending direction. The jaw also has a plurality of forward sweeping rope gripping features when operated in the ascending direction. A friction increasing descent assist device is provided on the powered rope ascender. The friction increasing descent assist device configured to provide a rope path having at least three guide surfaces around which the rope wraps angularly including a first, superior guide surface, a second laterally spaced capstan guide surface, and a third inferior guide surface. The friction increasing descent assist device enhances operation of the powered rope ascender when operating in the descending mode.
In specific embodiments, the friction increasing descent assist device is positioned on the powered rope ascender in an inferior direction from the at least one rope pulling jaw when the powered rope ascender is in use. The first and third guide surfaces may optionally form superior and inferior ends of a retention loop. The retention loop can comprise a gate, allowing a middle portion of rope to be engaged with the friction increasing descent assist device through the gate. The retention loop can optionally ensure that a rope stays engaged within the friction increasing descent assist device regardless of whether a free end of the rope is arranged in an optimal rope entry path while descending. The second guide surface can optionally be provided on a capstan peg that is laterally spaced from the retention loop. The friction increasing descent assist device can optionally be configured to provide a rope path that includes a rope wrap angle around the second guide surface that is greater than 180 degrees. The friction increasing descent assist device can optionally be configured to provide a rope path that includes a rope wrap angle around the second guide surface that is greater than 90 degrees. The friction increasing descent assist device can optionally be configured to provide a sum of rope wrap angles around the guide surfaces that is greater than 360 degrees.
In a second aspect, a device of the invention can include a retention loop through which a bight of rope can be inserted, and a capstan peg around which the bight can be looped.
The device can further include mounting features such as screw holes, bosses, pockets, or ridges that enable it to physically mount onto the body of a powered ascender, such that when it is mounted onto an ascender, it can resist forces imparted upon it during descent by the taut ropes it is descending.
The device can further include one or more rounded surfaces around which the rope is wrapped such that when a tension is imparted to the free end of the rope, by its own weight or otherwise, a magnified tension is produced on the other side of the surface via the capstan effect, and a frictional drag force is imparted on the rope which opposes the direction of motion of the device along the rope.
A device of the invention can be configured as a descent assist device on a powered ascender.
Further aspects of the invention will become clear from the detailed description below.
The present invention can be more easily understood and better appreciated when taken in conjunction with the accompanying drawings, in which:
Referring now to
An alternative embodiment of the invention is illustrated diagrammatically in FIG, 2, where the frictional descent device 3 is positioned “above” the powered rope climbing device 2 as referenced with the taut end of the rope 4 still being the “top” of the chain of components described herein.
T
1
=T
2
e
(μθ),
where T1 is the tension required on the taut end 5 to pull the rope 12 through the device when T2 is the tension applied to the free end 5 of the rope 12, μ is the frictional coefficient between the rope 12 and the material of the frictional descent device 3, and θ is the angle of the wrapping of the rope 12 around the guide surface 11. The same frictional magnification happens as a result of the rope's 12 wrapping around the capstan 10 and any other such guide surfaces which the rope 12 may be wrapped at some angle. A person of ordinary skill in the art will note that if greater frictional drag force is desired from the descent device 3, they may choose to increase the total amount of angular wrap of the rope 12 around guide surfaces 11 or capstan pegs 10 by increasing the number of such features, by configuring the features so as to allow more angular wrap around the same number of features, or by increasing the tension imparted on the free end 5 of the rope 12 as it passes through the device 3.
For example, as illustrated, three guide surfaces are provided. The first guide surface is provided on the superior side 15 of the retention loop 13. The second guide surface is provided on the capstan peg 10. The third guide surface is provided on the inferior side 11 of the retention loop 13. More or fewer guide surfaces could be provided to achieve the desired, or a predetermined, amount of friction for a particular rope. For example, three capstan pegs 10 could he provided, a first superior peg to the right, a second middle peg to the left of the first peg, and a third inferior peg to the right of the second peg. Such a configuration would result in five friction enhancing guide surfaces to which the capstan equation could be applied.
Further, the guide surfaces could be provided on structures other than a retention loop and a capstan peg. In the three guide surface embodiment, three capstan pegs could be used. Still further, a rope guide could be designed with no loops and no capstan pegs, for example by building a groove into the body of the powered rope ascender having the desired number of guide surfaces.
The retention loop 13 essentially forms a rope cover that extends between the superior and inferior guide surfaces. This type of cover provides protection against the rope coming apart from the guide surfaces, while still allowing a bight of rope to be engaged to the friction device without having to feed an end of the rope through the device. A cover could also extend to the capstan peg, providing even more assurance that the rope would not come loose, but making it more difficult to engage the rope with the friction device. Something short of a cover could also be used. For example, a capstan peg or other guide surface could have a lip that helps to retain the rope.
The retention loop can also be gated, or itself be a gate, such that the loop opens for easy engagement of a middle portion or bight of rope, and closes to retain the engaged rope. For example, as illustrated in
The above, and below, embodiments are described with respect to a rope. As used herein, the term “rope” is intended to refer to any flexible, elongate element that has sufficient strength in tension to be able to work with a powered rope ascender.
A pulley 8 is also shown as part of the powered rope ascender 1. Such a pulley 8 may also be configured to perform the same purpose as the frictional descent device 3. Since the rope 12 is wrapped around the pulley 8 by some angle, if the pulley can be locked by some means to resist rotation when the powered rope ascender 1 is descending the rope 12, it will also impart a frictional drag force on the rope 12 which resists the motion of the powered rope ascender 1 along the rope, thereby acting also as a frictional descent assist device as described herein.
In use, the descent device 3 as described is not needed for climbing, and a user may choose to disengage the rope 12 from the device 3 while climbing to avoid a buildup of slack rope between the climbing mechanism 2 and the descent device 3.
In one exemplary use, the descent device 3 can be used with the powered rope ascender 200 shown in
The rotational motor 201 can also have speed control and/or a gearbox 202 associated with it to control the speed and torque applied by the rotational motor to the task of pulling a rope. These elements can be integrated into a single, controllable, motor module, be provided as separate modules, or be provided in some combination thereof. In one embodiment, speed control elements can be provided integrally with a dc rotational motor, while a separate, modular gearbox is provided so that the gearing, and thus the speed and torque characteristics of the rope pulling device, can be altered as desired by swapping the gears. A modified self-tailing mechanism 207 is connected to the rotational motor 201, through the gearbox 202. In a preferred embodiment of the invention, the self tailing mechanism 207 includes a pair of rotating self-taller jaws, and the surface of the rotating self-tailor jaws includes ridges oriented in a forward-spiraling fashion so as to engage the rope with increased force and improved efficacy as either the motor torque is increased, or the load on the rope increases. While the illustrated embodiment has two jaws, one jaw could also be employed.
The jaws include ridges 213, splines, or other rope engaging features that are oriented forward toward the direction of rotation (forward sweeping), such that increased back-force on the rope 208 (increased load) or increased torque on the jaws 207 pulls the rope 208 deeper into the V-groove formed by each set of ridges, and thereby the grip force on the rope is increased. In such an embodiment, the jaws 207 and/or ridges 213 can be configured so as to form a barrel having a surface characterized by anisotropic.
The ridges 213 function to maintain the tension on the rope 208 during the ascent due to the forward orientation of the ridges 213. However, when the device 200 is used for powered descent and the jaw rotates in the opposite direction, the rope can temporarily find space between the forward orientation of the ridges 213, potentially resulting in slippage of the rope and damage to the rope by subsequent and repeated re-engagement of the ridges. In use, the descent assist device 3 can be used to obviate, or minimize any slippage during the descent while using a powered descent device 200, or like device.
This application claims benefit under 35 U.S.C. §119(e) of U.S. Provisional Patent Application Ser. No. 61/861,577, filed Aug. 2, 2013, herein expressly incorporated by reference in its entirety.
| Number | Date | Country | |
|---|---|---|---|
| 61861577 | Aug 2013 | US |
